There's a lot of other tax incentives/decentives to think of aswell. If you rent then live in a house, you're up for pro-rata capital gains from the time you weren't living in it, and i'm not sure how room mates work either. Way way simplier if they just pay cash of course. "what room mates? me and my missus were just living alone in this 5 bedroom house?"
And i've quoted the wrong post of yours.
Borg warner twins are a muhc better way to go for that sort of setup, supposedly. Or a similar power single is better, or a similar sized precision is better. or something.